A variety of authentication systems has been implemented. Such authentication systems have become increasingly important with the prolificacy of IT technologies in society, and with growing need for high-level security in social activities involving IT technologies.
FIG. 1 illustrates a semiconductor unit used in conventional authentication systems. This semiconductor unit comprises a semiconductor device 11 including a first IC chip CH1 having data processing functions, all packaged in a plastic mold, and a semiconductor device 12 including a second IC chip CH2 which contains confidential data like personal code, fingerprint data, and an encryption key, all packaged in a plastic mold. These semiconductor devices 11 and 12 are electrically connected by connecting the lead pins L1 of the semiconductor device 11 with the corresponding lead pins L2 of the semiconductor device 12 using a printed pattern W1.
In this way the semiconductor unit has a two-package structure and data are transferred between them through the printed pattern W1. This type of semiconductor units have a drawback that the confidential data may be easily retrieved from the second IC hip CH2 of the semiconductor device 12 for illegitimate analysis by use of a memory accessing technology. For example, the data can be analyzed by detecting signals passing through the lead pins L1 and L2 across the printed pattern W1.
Improvements have been made by the inventor of the present invention to circumvent the problem pertinent to the conventional authentication system as shown in FIG. 1. In one improvement, a semiconductor device 13 for use in authentication system includes an IC chip having an embedded memory as shown in FIG. 2, and in another improvement a semiconductor has a multi-chip structure 14 as shown in FIG. 3.
The semiconductor device 13 shown in FIG. 2 has a non-volatile memory MA, as indicated by a broken line, for storing confidential data embedded in an IC chip CH1 that has data processing function. The semiconductor device 13 is packaged by sealing it with a molding resin.
The semiconductor device 14 shown in FIG. 3 includes a first IC chip CH1 having a data processing function, and a second IC chip CH2 having a memory for storing confidential data. These IC chips are electrically connected together by connecting the corresponding connection pads P1 and P2 of the respective IC chips by means of bonding wires W2. The entire device is then packaged by sealing it with a molding resin. L1 represents lead pins of the package.
As such, the confidential data stored in the non-volatile memory MA and in the second IC chip CH2 of these semiconductor devices 13 and 14 are not accessible for illegitimate analysis. However, one can open the resin package if he has a technique to open a molded package and can probe the lead wires and/or pads connected to the non-volatile memory MA or the IC chip to read the confidential data. After all therefore, like any other conventional semiconductors as shown in FIG. 1, even improved semiconductor devices 13 and 14 can be attacked by illegitimate accesses for the confidential data, although the data are stored in the sealed non-volatile memory MA and/or sealed IC chip CH2.